Your Dashboard
Interview Coaching
Learn
System Design
ML System Design
Code
Behavioral
Salary Negotiation
Interview Guides
Search
⌘K
Get Premium
Leetcode 1639. Number of Ways to Form a Target String Given a Dictionary
Count the number of ways to form target left-to-right by picking each target character from some word’s character at column k, with the constraint that once you use column k you cannot use any column ≤ k thereafter (columns must be strictly increasing). This is a combinatorics/DP problem that uses per-column letter frequencies to count valid sequences of column-and-word choices, returning the result modulo 10^9+7.
Question Timeline
See when this question was last asked and where, including any notes left by other candidates.
All Regions
Comments
Hello Interview Premium
Your account is free and you can post anonymously if you choose.